Tables 1 and 2 present baseline demographic comparisons of non-users versus initiators. As indicated, the initiator group was very slightly but not significantly older at baseline. The groups are matched on estimated IQ scores, sex distribution, ethnicities, background socioeconomic indicators as well as self-reported externalizing. The sample is largely Caucasian and from middle to upper-middle class backgrounds as reflected by parental education (college-level) and family incomes (see Table 1). At baseline, future alcohol initiators reported marginally higher levels of MPQ Aggression (a facet of Negative Emotionality and a second-order facet of Constraint) as well as significantly lower levels of Traditionalism (see Table 2). Otherwise, the groups were indistinct in terms of major trait domains of personality.
